It is standard to provide a gas-control valve assembly with a safety-shutoff system that comprises a thermoelectric sensor positioned at the flame fed by the valve, a safety cutoff valve, and a solenoid system that holds the cutoff valve open so long as the sensor detects heat. To start, the valve knob is typically pressed in against a spring force to override the safety cutoff so that gas can flow to the burner and be ignited, whereupon the heat detected by the sensor will actuate the solenoid to hold the safety valve open and allow the knob to be released. If the burner does not ignite, releasing the knob will cut off gas flow, and if the burner goes out at a later time, the safety cutoff will close to cut off gas flow.
While such a system is well known and considered fairly intuitive and user-friendly, it has the disadvantage that the valve-control knob must be offset sufficiently from the control panel or the like it is mounted on that it can be depressed to override the safety shutoff. This creates an unattractive appearance with the control knob normally standing out, well offset from the surface it is mounted on.
German 29 43 996 proposes a rotary system where the safety shutoff is operated by a cylindrically tubular cam so that rotary action effects the necessary axial displacement to open the shutoff. While operating this system is somewhat easier, not requiring the so-called biaxial movement of both pressing and turning the knob, the knob still moves axially and thus presents the unattractive standing-off appearance of the prior-art systems.